Repairing A Twisted Prius Display Computer

This one is from way back in 2007, but the steps [hobbit] took to evaluate and repair a failed Prius Multi-Function Display (MFD) is a refresher course in how to go about fixing stuff that’s broken.

The 2004 / 2005 models of the Prius had peculiar problems with their MFD. Buttons and touch functions became sluggish and unresponsive, it wouldn’t display ECU data such as current and average fuel consumption, and couldn’t control stereo and air-conditioning. Lots of Prius users were reporting similar problems on the Priuschat forum.

The issues would usually arise long after warranty expired, and replacement units cost a couple of thousand dollars new. Toyota knew what the problem was (PDF link), but their fix involved swapping the defective units out.

[hobbit] managed to get a defective MFD unit from a friend, and because his own Prius still had a working MFD, he was able to carry out comparative tests on both units. The broken unit was generally laggy, and the buttons didn’t beep when pressed. Apparently, the AVCLan, a small data network between various components in the car, wasn’t reaching the MFD reliably. The MFD would send the “beep” command to the audio amplifier and wait for a confirmation that would never arrive. The system hung here until the MFD timed out.

In the end, the cause of the problem was the 60-pin micro connector that interfaces the two main boards of the MFD. Once the two are mated, tightening the mounting screws twisted the two boards ever so slightly, leading to flaky contacts.

The fix? [hobbit] tweaked all of the 60 pins outwards enough that they still made contact even when the connector housing got twisted. Comparing the defective MFD to the one in [hobbit]’s own car also demonstrated how the factory fixed the problem.

Thanks to [Nick] for sending in this tip, which he stumbled upon “while searching for ideas for a very small solder tip to repair something on my laptop.”

16 thoughts on “Repairing A Twisted Prius Display Computer

  1. And the old LED HP calculators had connectors between PCBs that would go soff. The fix was to disassemble the calculator and slip a tiny blade inside the male contacts and spread them out a tiny bit.

      1. PATA was mostly designed around slower electronics that ran at speeds where the RF characteristics of the connection were not of great concern. SATA is a bit more like Ethernet and handles the RF much better. Fewer traces is just one more reason the change made sense.

        PCI vs PCIe would be another good comparison.

  2. I have a better solution to this problem. Don’t buy a polluting piece of crap which causes severe and irreperable damage to the environment when the chemicals for its batteries are refined and processed in other countries – Batteries which must be replaced after a few years (especially in the very cold and very hot parts of the country) at the cost of a new engine or transmission. Every person I know with a prius (except those in hippie CA) who have purchased one, regret it. Do the math – You will be doing much less damage to the environment if you buy a small fossil fuel car – The VW TDI engines (including the so-called “cheater” ones) will have a smaller overall environmental footprint, and such fossil vehicles will outlast the prius by a decade or more. Stop falling for this al-gore sham! If there are any real engineers on this site who actually do the math before they buy a vehicle, then they know I speak the truth!!!

    1. Why are you still repeating this long disproven propaganda? Those claims against the Prius were thoroughly refuted eight years ago. The slight increase in manufacturing environmental impact is vastly overshadowed by the impact reductions resulting from the efficiency gains the battery enables. And unlike you, I can actually prove it:

      Quit trying to push your lies and propaganda. Nobody buys it anymore.

    2. My 2006 Prius has 439000km, 13 years old. It run for 418000km without ANY failure, and the first one was the battery that I refurbished by myself. Which kind of Prius are you talking about? may one sponsored by VW?

      BTW: I am a REAL engineer.

  3. That seems to be a common theme with Toyota: The root cause is a flawed design, but their fix is to replace the whole unit at a high cost.

    I had a highlander with the heating controls not working right. The OEM fix was $1500. The flaw was the knob potentiometer didn’t have a post to keep from rotating; it relied on the nut staying tight enough to keep from rotating. Also, the ribbon from it to the circuit board was barely long enough so any twisting would break the wires.

    To fix it, I took a few hours to remove the unit, open it up (toyota will *never* do that!), remove the ribbon, replace with 3 longer wires, resolder, tighten the nut & locktite so it doesn’t loosen. The real fix would be to use a pot that cannot rotate if the nut is loose and use a ribbon that is 1/16″ to 1/8″ longer so it’s not constantly under tension. But that will eliminate $1500 repairs and the profit from markups.

  4. Toyota is offering an extended warrantee fix for this problem. My 2007 Prius just started having the “black dash” problem and I found references in PriusChat to the service order for this. The big hassle is the dealer has to have proof of the problem, i.e. seeing it or seeing a video of it.

  5. Hello, Paola here,
    My Prius just lost its audio display (Sept. 2020) after jump-starting a battery (even though it wasn’t the first jump-start).
    Toyota service person said that a new unit will cost me… almost C$11,000… (I have not seen that high a quote reported before, on any forum).
    I looked for an alternative. Visions Electronics do offer substitute displays+radio, from C$2,500 up.
    I also found a repairman – the only one who does audio diplays in Vancouver, B.C. area. He needed to get the unit out to see whether it was DVD-based navigation or a hard drive (I had no clue: there’s no info in my papers, and mine was the latter). The repairman offered either [1] a used unit, CS$1,200+shipment+brokerage+customs +work, or [2] a 2014 unit for C$1,500+shipment+brokerage+customs+work (that was my choice)…
    Look at this: “RepairPal Fair Price Estimate $88 – $111” …. ????? HOW MUCH? WHAT A BLOODY JOKE!!!!
    More interestingly, in a chat, the repairman said that, from what he knows, the low voltage in a depleted basic battery may cause audio display to fail (my discovery: before jump-starting, learn which your audio display fuse is, and pull it out!!!). However, he heard that the Prius models do have a device that is supposed to retain the voltage, or prevent low voltage from affecting the audio display, but, for some reason, this device has not been working.
    (And again, we – the customers, are to pay for this designed fault, as some here paid for poor soldering on early 2000 models!). Anyone for class action?

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